1. Field of the Invention
The present invention relates to a lens actuator for moving a lens, and to an electronic device using the lens actuator, such as a camera and a portable telephone.
2. Background Art
In recent years, an increasing number of electronic devices incorporating a lens, such as a camera and a portable telephone, have been making auto-focusing operation of the lens, using a lens actuator. In association with this, with the downsizing of the electronic devices, lens actuators that can be downsized and operated in a stable manner are required. Such conventional lens actuator 130 is described with reference to FIGS. 7 through 9.
FIG. 7 is a sectional view of conventional lens actuator 130. FIG. 8 is an exploded perspective view of lens actuator 130. As shown in FIGS. 7 and 8, lens actuator 130 includes substantially cylindrical carrier 111 made of insulating resin, cover 112 made of insulating resin, and case 113 made of insulating resin. A lens (not shown) is fitted in a hollow portion of carrier 111. Carrier 111 is housed between case 113 and cover 112 covering the top face of the case so as to be movable vertically.
Further, lens actuator 130 includes upper spring 114 and lower spring 115 each made of a thin metal sheet. Upper spring 114 is provided between the bottom face of cover 112 and the top face of carrier 111. Lower spring 115 is provided between the bottom face of carrier 111 and the inner bottom face of case 113. Each of upper spring 114 and lower spring 115 is disposed in substantially a bending state. Carrier 111 is held in a predetermined position by upper spring 114 and lower spring 115 in resilient contact with the top and bottom faces of the carrier, respectively.
Further, lens actuator 130 includes coil 116 made of a copper alloy wire wound in substantially an annular shape, and yoke 117 formed in substantially cylindrical shape using iron or the like. Coil 116 is fixed on flange 111A under the outer periphery of carrier 111. Yoke 117 having substantially a U sectional shape is disposed in case 113 around the outer periphery of carrier 111 to cover coil 116.
Further, lens actuator 130 includes a plurality of magnets 118 formed in substantially arc shapes. Magnets 118 are attached to the inner wall surface of yoke 117 on the outer peripheral side thereof.
FIG. 9 is a partially sectional view of conventional lens actuator 130. Magnet 118 is magnetized in the horizontal direction (radial direction of the lens) in FIG. 9. Thus, as shown by the arrows in FIG. 9, a magnetic path from magnet 118 to yoke 117 and coil 116 is formed. Clearance L of approximately 0.2 mm is provided between the inside wall surfaces of magnets 118 on the inner peripheral side thereof and the outer peripheral side face of coil 116, and between the inner peripheral side face of coil 116 and the inner wall surface of yoke 117 on the inner peripheral side thereof so that coil 116 is vertically movable.
Both ends of the winding of coil 116 are coupled to a plurality of electrodes 119 made of a copper alloy or the like by soldering, with a slack provided for vertical movement. The bottom faces of electrodes 119 project downwardly from the bottom face of case 113. Spacer 120 made of insulating resin is disposed on lower spring 115.
Then, lens actuator 130 thus structured is incorporated into an electronic device, such as a camera and a portable telephone. The plurality of electrodes 119 are coupled to the electronic circuit (not shown) of the electronic device.
In the above structure, the operation of a push button (not shown) of the electronic device applies voltage to electrodes 119 through the electronic circuit and feeds current through coil 116. Then, as shown in FIG. 9, coil 116 having a magnetic field in the horizontal direction formed therein receives vertical force orthogonal to the magnetic field. This force moves coil 116 and carrier 111 having coil 116 fixed thereto in the vertical direction, thus making auto-focusing operation. Thereby, the focus of the lens fitted in carrier 111 can be adjusted.
When the current supplied to coil 116 is shut down, the urging force of upper spring 114 and lower spring 115 fixed on the top and bottom face of carrier 111, respectively, pushes carrier 111 back to the predetermined position.
The technique related to such lens actuator 130 is disclosed in Japanese Patent Unexamined Publication No. 2004-280031, for example.
As described above, in conventional lens actuator 130, clearance L need be provided so that the vertical movement of coil 116 is not hindered by the contact of coil 116 with magnet 118 or yoke 117 that may be caused dimensional variations of respective components or displacement in assembly thereof. This clearance L need be provided on both inner and outer peripheral sides of coil 116. Further, the thickness of yoke 117 on the inner peripheral side added thereto makes it difficult to downsize lens actuator 130 in the radial direction thereof.
Because coil 116 makes vertical movements, a certain degree of slacks are necessary at both ends of the winding of coil 116. Further, it is necessary to solder the ends of the winding to electrodes 119 with a slack provided at both ends so that breaks are prevented. Because of these factors, treatment of both ends of coil 116 and assembly take time and effort. Repeated operations may cause breaks, thus destabilizing these connections.